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SSC Sample Paper SSC CGL - Sample Paper-12

  • question_answer
    A work can be completed by P and Q in 12 days, Q and R in 15 days, R and P in 20 days. In how many days P alone can finish the work?                                   

    A) 10                                

    B) 20      

    C) 30                    

    D) 60

    Correct Answer: C

    Solution :

    (P + Q)s 1 day?s work \[=\frac{1}{12}\]               ?(i) (Q + R)?s 1 day?s work \[=\frac{1}{15}\]              ? (ii) (R + P)?s 1 day?s work \[=\frac{1}{20}\]              ? (iii) Adding all three Eqs. 2(P + Q + R)?s 1 day?s work \[=\frac{1}{12}+\frac{1}{15}+\frac{1}{20}=\frac{5+4+3}{60}=\frac{12}{60}=\frac{1}{5}\] \[\therefore \] (P + Q + R)?s 1 day?s work \[=\frac{1}{10}\]            ? (iv) \[\therefore \] P?s 1 day?s work = Eq. (iv)\[-\]Eq. (ii)             \[=\frac{1}{10}-\frac{1}{15}=\frac{3-2}{30}=\frac{1}{30}\] \[\therefore \] P along will complete the work in 30 days.     


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